Hey there, I recently picked up a '74 DT125 with a crunchy bottom end. Ripped it all apart, took photos of everything but when splitting the cases I had 2 metal balls fall to the ground, no clue where they came from and where I should put them back. Any advice is greatly appreciated!
  

Greetings from Tennessee. #18 is to your clutch rod and #12 to your neutral switch it should also have a spring

Where did the two short pins come from in your pic. Look like are from the selector drum if you've removed the end plate. Otherwise the way they're sitting with the ball i was starting to wonder if someone had made a clutch pushrod in two pieces & added a ball between. Your neutral detent ball & spring i can still see the cap in the case so remove that & fit it last after assembling the center cases. Ideally that should have been removed with spring & ball before the center cases are parted--must be a spring there somewhere or still in the cap. Should be a ball between the long pushrod & a short mushroom rod.

My first thought was you said crunchy bottom end so check your crank bearings to see if they came apart or any other bearing for that matter. Main axle bearing? I'd be replacing all the bearings anyway. Good luck!

Yes they are from the selector, thanks for the heads up on removing it before I split the cases my first time ever doing this and was following some guy from Taiwan on youtube haha. I found the spring at the bottom of the case.

Thank you @Ht1kid for the diagram and information, major help. The bearings are all intact, in amazing condition actually, just one of the crank bearings is oddly extremely rusted and crunchy.

heres a partzilla link to all pages just incase it helps. model changed design in 74 but looks like old design as think electric start retained the old cases. we had both kick & electric in NZ, but anyway, goodluck. ps, those pins didn't need to come out but hope you've saved all of them. there's one short one too but that won't fall out as has a tiny circlip.
www.partzilla.com/catalog/yamaha/motorcycle/1974/dt125a

Hey there, back with another question. Well 2 actually. 

I've searched online and in the service manual yet cant find any info on how to take the crank itself apart to replace the lower end bearing on it.  imgur.com/a/WSE63vY  I can't seem to post photos today so there's a link to it. I'm assuming I just punch the center out or do i need to have it pressed out or is there another way that I don't know about and cant find?

Also I'm having trouble getting that bolt out of the armature that I used to press it off of the crank. I was reading after the fact to taper the threads and make it easier to get out but its STUCK on there now... any recommendations? 

I'd guess the end of the bolt has flared from working hard to pull the armature off the taper. Probably can't do much now except force it back. Otherwise can you cut the head off the bolt then put armature in the lathe & machine the bolt stem down to below thread size the wind it through & out the far end. Never had to do it but i'm full of smart arse ideas the usually don't work lol.

With the crank, you're getting into specialized territory there but sounds like you're keen to get right into it. Here's a random video that should be good to watch.

Thank you for the link to that video! I feel like I'm a bit over my head in this but that's cause I've never done it before. I don't have a press to get that pin out with... or the money for one. Might just got to a shop and see if they can get it out or maybe see if there is a hydraulic press on my campus I could bum. As for the armature I'll google a bit more to see if I can find anything, will keep everyone updated!